Samsung AM18A1C09 Owner's Instructions & Installation Manual page 34

There are two refrigerant pipes of different diameters:
A smaller one for the liquid refrigerant
A larger one for the gas refrigerant
A short length of piping is already fitted to the air conditioner. You
must extend this piping using assembly piping (optionally supplied).
The connection procedure for the refrigerant piping varies according
to the exit position of the piping from the indoor unit, as seen when
facing the air conditioner in position on the wall:
Right (A)
Left (B)
Underside (C)
Rear
The piping will be insulated and fixed permanently into
position once the whole installation has been tested for
gas leaks; refer to page 42 for further details.